Synthetic method of ketol unsaturated fatty acids

ABSTRACT

The present invention provides an efficient synthetic method of α-ketol unsaturated fatty acid having a double bond at a β-position to the ketone group thereof. It comprises the steps of: preparing compound (4) by reacting monosubstituted acetylene (2) with epoxide (3); and preparing α-ketol unsaturated fatty acid (1) from said compound (4) as shown in Reaction Formula 1:  
                 
 
     wherein R 1  represents an alkyl group of 1-18 carbon atoms or an aliphatic hydrocarbon group of 2-18 carbon atoms having 1-5 double or triple bonds at given positions; R 2  represents a protecting group for a hydroxyl group; R 3  represents a protecting group for a carboxyl group; R is identical to R 1  or, when R 1  has one or more triple bonds, represents an aliphatic hydrocarbon group in which each triple bond of R 1  is converted to a double bond; and A represents an alkylene group of 1-18 carbon atoms.

FIELD OF THE INVENTION

[0001] This invention relates to a synthetic method of an α-ketolunsaturated fatty acid and, in particular, to improve the yield in asynthesis of an α-ketol unsaturated fatty acid having a double bond at aβ-position to the ketone group thereof.

BACKGROUND OF THE INVENTION

[0002] Heretofore, various actions of ketol fatty acids have been knownin the art, and in recent years it has been reported that some of ketolfatty acids have a flower bud formation inducing effect (JapaneseUnexamined Patent Publication Nos. 9-295908 and 11-29410).

[0003] Several attempts have been made for preparing ketol fatty acidsefficiently. As in the case of α-ketol unsaturated fatty acid (1)represented below, however, due to a double bond existing at aβ-position to the ketone group there is a problem that it is hard to beefficiently prepared by organic synthetic methods.

[0004] As for examples of synthetic methods of α-ketols, the followingReaction Formulae I to III may be provided.

[0005] The Reaction Formula I shows a method to provide α-ketol (12) bycondensing acid chloride (10) and aldehyde (11) in the presence ofsamarium iodide (Tetrahedron Letters, Vol. 33, No. 19, 2621-2624 (1992),and Tetrahedron Letters, Vol. 35. No. 11, 1723-1726 (1994)). However,Reaction Formula I provided only a complicated mixture as a resultingproduct. Furthermore, the purification of such a product only gavecompound (13) in which the double bond of α-ketol (12) was transferredat low yield, so that Reaction Formula I could not allow the isolationof desired α-ketol (12).

[0006] The Reaction Formula II shows a method that dithiane (14) isconverted into its lithio-derivative by a lithiation process using alkyllithium such as n-butyllithium and then the lithio-derivative iscondensed with aldehyde (11) to provide compound (15), followed byconverting a dithio part of compound (15) into a carbonyl group toobtain an α-ketol (12) (J. Org. Chem., Vol. 33, No. 1, 298-300 (1968),and J. C. S. Chem. Comm., 100-101 (1979)). In this case, however, theresultant was also a complicated mixture, so that the target compoundcould not be isolated therefrom.

[0007] The Reaction Formula III shows a method using methylthiomethylp-tolylsulfone derivative (16) which anions may present more stable thanthose of the dithiane. Namely, the methylthiomethyl p-tolylsulfonederivative (16) is reacted with aldehyde (11) just as in the case ofReaction Formula II to provide compound (17), followed by converting athiomethylsulfone part of compound (17) into a carbonyl group to obtainα-ketol (12) (Tetrahedron Letters, Vol.27, No.31, 3665-3668 (1986), andTetrahedron Letters, Vol. 24, No. 51, 5761-5762 (1983)). In this method,compound (17) could be isolated but the yield was extremely low as 20%or less. Also, subsequent conversion reaction to a ketone gave acomplicated mixture, so that the isolation was extremely difficult.

[0008] Thus, in the case of α-ketol unsaturated fatty acid in which adouble bond is present at a β-position to the ketone, the yield of itsskeleton-forming reaction is extremely low as the double bond may beeasily transferred. This is the reason why it is hard to obtain thedesired α-ketol unsaturated fatty acid efficiently.

SUMMARY OF THE INVENTION

[0009] The present invention has been accomplished in view of the aboveproblems of the prior art. It is, therefore, a object of this inventionto provide a method for efficiently synthesizing α-ketol unsaturatedfatty acid having a double bond at a β-position to the ketone.

[0010] As a result of the diligent studies conducted by the inventorsfor attaining the above object, it has be found that by a reactionbetween a monosubstituted acetylene and an epoxide a carbon skeleton ofα-ketol unsaturated fatty acid can be formed efficiently. Thus, thepresent invention has been accomplished.

[0011] Namely, a method of synthesizing an α-ketol unsaturated fattyacid in accordance with the present invention comprises the steps of:

[0012] preparing compound (4) by reacting monosubstituted acetylene (2)with epoxide (3); and

[0013] preparing α-ketol unsaturated fatty acid (1) from said compound(4), as shown in the following Reaction Formula 1:

[0014]  wherein

[0015] R¹ represents an alkyl group of 1-18 carbon atoms or an aliphatichydrocarbon group of 2-18 carbon atoms having 1-5 double or triple bondsat given positions;

[0016] R² represents a protecting group for a hydroxyl group;

[0017] R³ represents a protecting group for a carboxyl group;

[0018] R is identical to R¹ or, when R¹ has one or more triple bonds, Rrepresents an aliphatic hydrocarbon group in which each triple bond ofR¹ is converted to a double bond; and

[0019] A represents an alkylene group of 1-18 carbon atoms.

[0020] The method of the present invention preferably comprises thesteps of:

[0021] reducing said compound (4) to produce compound (5);

[0022] oxidizing a hydroxyl group of said compound (5) to producecompound (6); and

[0023] deprotecting R² and R³ of said compound (6) to produce saidα-ketol unsaturated fatty acid (1), as shown in Reaction Formula 2:

[0024] wherein R¹, R², R³, R, and A are the same as defined in saidReaction Formula 1.

[0025] Also, the method of the present invention preferably comprisesthe steps of:

[0026] reducing said compound (4) to produce compound (5);

[0027] deprotecting R³ of said compound (5) to produce compound (7);

[0028] oxidizing a hydroxyl group of said compound (7) to producecompound (8); and

[0029] deprotecting R² of said compound (8) to produce said α-ketolunsaturated fatty acid (1), as shown in Reaction Formula 3:

[0030] wherein R¹, R², R³, R, and A are the same as defined in saidReaction Formula 1.

[0031] In the present invention, R¹ preferably represents R⁴—C≡C—CH₂—,where R⁴ represents an alkyl group of 1-7 carbon atoms.

[0032] R⁴ preferably represents ethyl group.

[0033] “A” preferably represents an alkylene group expressed by—(CH₂)n—, where n is an integer of 1 to 10.

[0034] “n” is preferably 7.

[0035] R² preferably represents an ether-type protecting group.

[0036] The double bond of α-ketol unsaturated fatty acid (1) preferablyhas a cis-configuration.

[0037] An intermediate for synthesis of α-ketol unsaturated fatty acid(1) in accordance with the present invention is represented by thegeneral formula (4):

[0038] wherein

[0039] R¹ represents an alkyl group of 1-18 carbon atoms or an aliphatichydrocarbon group of 2-18 carbon atoms having 1-5 double or triple bondsat given positions;

[0040] R² represents a protecting group for a hydroxyl group;

[0041] R³ represents a protecting group for a carboxyl group; and

[0042] A represents an alkylene group of 1-18 carbon atoms.

[0043] In a method of synthesizing an optically active α-ketolunsaturated fatty acid in accordance with the present invention, it ispreferably that in any methods mentioned above an asymmetric carbon atomof —C(OR²)— in said epoxide (3) has either of R-configuration orS-configuration and that an asymmetric carbon atom in the α-ketolstructure of α-ketol unsaturated fatty acid (1) has either ofR-configuration or S-configuration.

[0044] Also, the method preferably comprises the steps of:

[0045] preparing compound (4A) by reacting said monosubstitutedacetylene (2) with (R)-epoxide (3A) obtained from compound (21A) whichasymmetric carbon atom at an aryl position has R-configuration; and

[0046] preparing (R)-α-ketol unsaturated fatty acid (1A) from saidcompound (4A), as shown in the following Reaction Formula 1A:

[0047] wherein R¹, R², R³, R, and A are the same as defined in saidReaction Formula 1.

[0048] Also, the method preferably comprises the steps of:

[0049] preparing compound (4B) by reacting said monosubstitutedacetylene (2) with (S)-epoxide (3B) obtained from compound (21B) whichasymmetric carbon atom at an aryl position has S-configuration; and

[0050] preparing (S)-α-ketol unsaturated fatty acid (1B) from saidcompound (4B), as shown in the following Reaction Formula 1B:

[0051] wherein R¹, R², R³, R, and A are the same as defined in saidReaction Formula 1.

[0052] An optically active intermediate for synthesis of said α-ketolunsaturated fatty acid (1A) or (1B) is represented by the generalformula (4A) or (4B):

[0053] wherein

[0054] R¹ represents an alkyl group of 1-18 carbon atoms or an aliphatichydrocarbon group of 2-18 carbon atoms having 1-5 double or triple bondsat given positions;

[0055] R² represents a protecting group for a hydroxyl group;

[0056] R³ represents a protecting group for a carboxyl group; and

[0057] A represents an alkylene group of 1-18 carbon atoms.

BEST MODES FOR CARRYING OUT THE INVENTION

[0058] In Reaction Formula 1, R¹ of monosubstituted acetylene (2)represents an alkyl group of 1-18 carbon atoms or an aliphatichydrocarbon group of 2-18 carbon atoms having 1-5 double or triple bondsat optional positions therein.

[0059] The alkyl group may be either of a straight or a branched chain.Examples thereof include methyl, ethyl, propyl, butyl, pentyl,isopropyl, tert-butyl, hexyl, octyl, decyl, tetradecyl, octadecyl,1-methylpropyl, 1-ethylpropyl, 3-methylbutyl, and 2-ethylhexyl.Preferably, the alkyl group has 1-10 carbon atoms.

[0060] The aliphatic hydrocarbon group having double or triple bonds maybe either of a straight or a branched chain, where these multiple bondsdo not limited to specific positions. The aliphatic hydrocarbon grouphas preferably 1-10 carbon atoms including one triple bond, and morepreferably a group represented by R⁴—C≡C—CH₂—. R⁴ represents an alkylgroup of 1-7 carbon atoms, and preferably ethyl group.

[0061] A protecting group R² for a hydroxyl group and another protectinggroup R³ for a carboxyl group in epoxide (3) are not limited, unless anytrouble is caused in the synthetic method of the present invention.Examples of the protecting group R² include ether-type protecting groupssuch as methoxymethyl (MOM), 2-methoxyethoxymethyl (MEM),tetrahydropyranyl (THP), 1-ethoxyethyl, tert-butyl, benzyl,trimethylsilyl (TMS), and tert-butyldimethylsilyl (TBDMS); ester-typeprotecting groups such as formyl, acetyl, and benzoyl; carbamate-typeprotecting groups such as benzyloxycarbonyl; and sulfonyl-typeprotecting groups such as p-toluenesulfonyl. Among them, it ispreferably the ether-type protecting group, and more preferably MOM, MEMor TBDMS.

[0062] As for the protecting group R³, for example, methyl, ethyl,tert-butyl, benzyl, methoxymethyl (MOM), 2-methoxyethoxymethyl (MEM), ortetrahydropyranyl (THP) can be used.

[0063] In Reaction Formula 1, “A” represents a straight or branchedalkylene group of 1-18 carbon atoms, preferably a straight alkylenegroup of 1-10 carbon atoms, and more preferably —(CH₂)₇—.

[0064] According to the synthetic method of the present invention,compound (4) is prepared as an intermediate by reacting monosubstitutedacetylene (2) with epoxide (3), and then desired α-ketol unsaturatedfatty acid (1) is obtained from compound (4). “R” of α-ketol unsaturatedfatty acid (1) is derived from R¹ of monosubstituted acetylene (2) usedas a starting material. R may be identical to R¹ or, if R¹ has one ormore triple bonds, an aliphatic hydrocarbon group in which such triplebonds are converted into double bonds.

[0065] In the present invention, unless otherwise specified, R¹, R², R³,R³, R, A, and n are defined as described above.

[0066] Although each double bond in α-ketol unsaturated fatty acid (1)may be either of cis- or trans-configuration, in view of a effect suchas a flower bud formation inducing effect or the like, acis-configuration is preferable. Also, there is at least one asymmetriccarbon atom in α-ketol unsaturated fatty acid (1) of the presentinvention. The present invention includes each of optical isomers dependon the asymmetric carbon atom and a mixture thereof. In each syntheticstep of the present invention, using well-known methods an opticalresolution can be effected.

[0067] In Reaction Formula 1, the reaction between monosubstitutedacetylene (2) and epoxide (3) can be performed by converting themonosubstituted acetylene (2) into its 1-lithio derivative with anorganic lithium compound such as n-butyllithium or phenyllithium, andthen by reacting the derivative with epoxide (3). If required, a Lewisacid such as boron trifluoride etherate or a base such asethylenediamine or tetramethylethylenediamine may be added thereto. Asfor a solvent, tetrahydrofuran (THF), diethyl ether, dimethyl sulfoxide(DMSO), or the like can be used. The reaction is preferably performed ata low temperature of −50° C. or less.

[0068] In Reaction Formula 1, the reaction for converting compound (4)into α-ketol unsaturated fatty acid (1) includes reduction of triplebonds to double bonds, oxidation of a hydroxyl group, and deprotectionof R² and R³ in appropriate order. For example, As shown in ReactionFormula 2, after the reduction of triple bonds to double bonds, theoxidation of a hydroxyl group and the deprotection of R² and R³ areperformed successively. The order of deprotection of R² and R³ is notlimited and both R² and R³ may be removed by deprotection at the sametime depending on the species thereof. Also, as shown in ReactionFormula 3, it is possible to perform reduction of triple bonds to doublebonds, the deprotection of carboxyl-protecting group R³, the oxidationof a hydroxyl group, and the deprotection of R² in this order. However,Reaction Formula 2 is preferable.

[0069] For the reduction of compound (4), a selective reduction processshould be selected depending on a cis- or trans-configuration of eachdouble bond to be obtained. For example, a selective reduction fromtriple bonds to cis-double bonds can be performed by a catalyticreduction process using nickel acetate-NaBH₄ as a catalyst or anothercatalytic reduction process using Pd-CaCO₃ or Pd-BaSO₄ as a catalyst inthe presence of lead acetate or quinoline. As for a solvent to be used,alcohols such as methanol and ethanol, ethyl acetate, acetic acid,diethyl ether, benzene, hexane, dioxane, and the like can be used. Thereaction temperature may be in the range of room temperature to a refluxtemperature. Also, the above goal can be achieved by performing ahydroboration process with diborane to produce a corresponding vinylborane derivative and then hydrolyzing the derivative with acetic acidor the like. Furthermore, it can be achieved by a reduction processheating a material in methanol together with a zinc-copper alloy.

[0070] A selective reduction to trans-double bonds includes a processusing an alkali metal such as sodium, lithium, or potassium in an aminesolvent such as liquid ammonia, methylamine, ethylamine, orethylenediamine. As for a solvent in this case, in addition to the aminedescribed above, an alcohol, diethyl ether, THF, dimethoxyethane (DME),and the like can be used.

[0071] Any reaction for forming a carbonyl group of α-ketol inconversion from compound (5) into compound (6) or from compound (7) intocompound (8) can be performed by an oxidation of a hydroxyl group. Suchoxidation may be chromic acid oxidation, DMSO oxidation, or an oxidationusing dimethyl sulfide (DMS)/N-chlorosuccinimide (NCS), o-iodoxybenzoicacid, or the like.

[0072] In the chromic acid oxidation, chromic compounds includingchlomium oxide (VI), a dichromate such as potassium dichromate or sodiumdichromate, pyridinium chlorochromate (PCC), pyridinium dichromate(PDC), or pyridinium fluorochromate (PFC) can be used. In the case usingchromium oxide (VI) or a dichromate, for example, under an acidiccondition with sulfuric acid the reaction can be carried out in asolvent such as acetone, acetic acid, THF, dioxane, diethyl ether,benzene, chlorobenzene, or carbon tetrachloride. Also, there is ananother method using chrome oxide (VI)-pyridine complex in a solventsuch as pyridine or dichloromethane. In the case using a chrome compoundsuch as PCC, PDC, or PFC, the reaction can be carried out in a solventsuch as dichloromethane. In any event, the reaction temperature istypically in the range of 0 to 60° C.

[0073] In the DMSO oxidation, the reaction is typically carried out inthe presence of an appropriate electrophilic reagent. Depending on akind of the electrophilic reagent used, it can be broadly classified asDMSO-dicyclohexylcarbodiimide (DCC) method, DMSO-acetic anhydridemethod, DMSO-phosphorus pentoxide method, DMSO-sulfur trioxide-pyridinemethod, and so on. In the case of DMSO-DCC method, for example,additionally using pyridine-trifluoroacetic acid is used as a hydrogendonor, the reaction can be carried out in a solvent such as benzene ifrequired. The DMSO-acetic anhydride method is generally carried outwithout any solvent. The DMSO-phosphorus pentoxide method is carried outin a solvent such as dimethylformamide (DMF). The DMSO-sulfurtrioxide-pyridine method is carried out in the presence oftrimethylamine. In each of the cases, typically, the reactiontemperature may be in the range of room temperature to 70° C.

[0074] In the DMS/NCS oxidation, it is preferable that a DMS-NCS complexis prepared in toluene at 0° C. and then subjected to the oxidationprocess at 0° C. to −25° C.

[0075] In the oxidation using o-iodoxybenzoic acid, a solvent may beDMSO, a halogenated hydrocarbon such as chloroform or dichloromethane,an aromatic hydrocarbon such as benzene, xylene, or toluene. Thereaction temperature is typically in the range of room temperature to areflux temperature.

[0076] A deprotecting reaction of R² to be required for obtainingα-ketol unsaturated fatty acid (1) as a final product can be performedby well known methods such as described in “Protective groups in OrganicSynthesis”, T. W. Greene, and P. G. M. Wuts, John Wiley & Sons, Inc.,and so on, depending on a selection of the protecting group. If R² isTBDMS, for example, the deprotecting reaction can be carried out in asolvent such as acetonitrile, or water with hydrogen fluoride.

[0077] The deprotection of R³ also can be performed by well knownmethods, depending on a selection of the protecting group. In the casewhere R³ is an alkyl group such as methyl group, for example, thedeprotection can be performed by a hydrolysis using a base such aspotassium hydroxide or a sodium hydroxide in a solvent such as methanolor water. In addition, it is possible to perform the deprotection withan enzyme such as a lipase.

[0078] In each of the conventional methods represented by the respectiveReaction Formulae I to III as described above, a carbon skeleton ofα-ketol unsaturated fatty acid (1) is formed by a condensation reactionbetween a carbon of a carbonyl group and a carbon of C—OH group. In thesynthetic method of the present invention, on the other hand, an epoxide(3) having a 1,2-epoxy-3-hydroxy structure as a precursor of α-ketol isreacted with monosubstituted acetylene (2) to form a carbon skeleton ofα-ketol unsaturated fatty acid. According to the present invention,compound (4) to be an intermediate can be obtained in a high yield of85% or more and following steps are convenient, so that α-ketolunsaturated fatty acid (1) can be efficiently prepared as a finalproduct.

[0079] The monosubstituted acetylene (2) of Reaction Formula 1 can becommercially available or prepared by a well known reaction process. Forinstance, 1,4-heptadiyne can be prepared by reacting 1-butyne with ethylmagnesium bromide to produce a corresponding magnesium acetylide andthen reacting the latter with 3-bromopropane-1-yne (e.g., JapaneseUnexamined Patent Publication No. 53-34926, and J. Chem. Ecol., 4,531-542 (1978)). Another monosubstituted acetylene can be prepared inthe same way. Furthermore, it can be prepared by a dehydrohalogenationreaction of 1,2-dihalogenoalkane or halogenoalkene with a base, or adehlogenation reaction of tetrahalogenoalkane or dihalogenoalkene.

[0080] The epoxide (3) can be also prepared by a well known reaction. Arepresentative synthetic example will be shown bellow.

[0081] In Reaction Formula 4, the epoxide (3) can be obtained by:preparing an aldehyde (11) by a selective reduction of dicarboxylic acidhalfester (20-1) or by a reductive ozonolysis or a periodate degradationof compound (20-2); converting a formyl group of aldehyde (11) into aH₂C═CH—CH(OH)— group; performing an epoxidation of a double bond; andthen protecting a hydroxyl group. Although R⁵ of compound (20-2) may beany substituent unless otherwise effected on the reaction, it ispreferably an alkyl group.

[0082] The aldehyde (11) of Reaction Formula 4 can be obtained by eachof several methods. For example, the aldehyde (11) may be obtained byreacting dicarboxylic acid halfester (20-1) with 1,1-carbonyldiimidazolto obtain an acid imidazolide and then reducing the latter with lithiumaluminium hydride tri-tert-butoxide. These reactions can be typicallyperformed in an anhydrous solvent such as diethylether or THF at atemperature in the range of 0° C. to a reflux temperature.

[0083] Alternatively, aldehyde (11) can be obtained by reacting compound(20-2) with ozone to obtain an ozonide and then reducing the latter withdimethylsulfide or the like. This reaction can be typically performed inan organic solvent such as methanol at a temperature in the range of−80° C. to 0° C. As another method, furthermore, aldehyde (11) can beobtained by epoxidation of compound (20-2) with a peracid such asm-chloroperbenzoic acid and then reacting the resulting epoxide with aperiodic acid. The epoxidation is typically performed in an organicsolvent such as dichloromethane, hexane, ethyl acetate, diethylether, ormethanol at a temperature in the range of 0° C. to a reflux temperature.The reaction with the periodic acid is typically performed in an aqueousorganic solvent such as a mixture of dioxane with water at a temperaturein the range of 0° C. to a reflux temperature.

[0084] In a second stage, for example, by Grignard reaction using vinylmagnesium bromide aldehyde (11) can be converted into compound (21).This reaction is typically performed in an anhydrous solvent such asdiethylether or THF at a low temperature of −30° C. or less.

[0085] In a third stage, for example, compound (21) can be convertedinto compound (22) by epoxidation with a peracid. The peracid may beperbenzoic acid, m-chloroperbenzoic acid, peracetic acid, hydrogenperoxide, or the like. The solvent may be selected from hydrocarbonssuch as benzene and hexane, halogenated hydrocarbons such asdichloromethane and chloroform, esters such as ethyl acetate, etherssuch as diethyl ether and THF, alcohols such as methanol, and so on. Thereaction temperature is typically in the range of 0° C. to a refluxtemperature.

[0086] In a fourth stage, by protecting a hydroxyl group of compound(22) a desired epoxide (3) can be obtained. The protecting reaction canbe performed in a conventional manner depending on a selection of theprotecting group (e.g., “Protecting groups in Organic Synthesis”described above). If the protecting group is TBDMS or TMS, for example,the corresponding chlorosilane compound is used for the reaction in thepresence of a base such as pyridine, triethylamine, triethanolamine,urea, DBU, or imidazole. The reaction is typically performed in asolvent such as benzene or DMF at a temperature in the range of roomtemperature to a reflux temperature.

[0087] The optical isomer (1A) or (1B), in which the asymmetric carbonatom of α-ketol structure —COC(OH)— in α-ketol unsaturated fatty acid(1) has R- or S-configuration respectively, can be obtained by opticalresolution of α-ketol unsaturated fatty acid (1) prepared in the aboveReaction Formula 1. Alternatively, as shown in Reaction Formula 1A or1B, it can be synthesized by a reaction according to Reaction Formulae 1to 3 using an optically active epoxide (3A) or (3B). The epoxide (3A) or(3B) is an optical isomer in which the carbon at 3-position of1,2-epoxide-3-hydroxy structure being a precursor of α-ketol structurehas R- or S-configuration. The epoxide (3A) or (3B) can be synthesizedusing a well known reaction. For example, according to the third tofourth stages of the above Reaction Formula 4, it can be prepared froman optically active compound (21A) or (21B) in which an asymmetriccarbon atom of —C(OH)— is a R- or S-configuration.

[0088] The compound (21A) or (21B) can be obtained from racemic compound(21) thereof by a well known method. For example, a direct opticalresolution, which may be performed by a liquid chromatography using anoptically active column, can be used. Also, a method including: bindingthe compound (21) with an optically active compound by an ester bond orthe like to induce compound (21) to a diastereomer; separating thediastereomer by a well known process such as recrystallization,thin-layer chromatography, or liquid chromatography; and then breakingthe bond can be used. Furthermore, one of optical isomers (21A) and(21B) is reacted by an optically selective enzymatic reaction tocompound (21) and is removed as a reaction product, thereby obtainingthe other optical isomer.

[0089] As a representative example, the racemic compound (21) isselectively reacted with a vinyl acetate using an enzyme such as alipase to acetylate either the optical isomer (21A) or (21B), and then aseparation between a resulting acetylated isomer and an unacetylatedisomer is carried out, thereby obtaining an optical isomer (21A) or(21B). The present reaction is typically performed in an organic solventsuch as pentane or diisopropyl ether at a temperature in the range of−40° C. to 40° C.

[0090] Also, the isomer (21A) or (21B) can be obtained by adeacetylation of the acetylated isomer using a well known method. Forexample, there are methods for removing an acetyl group by an enzymesuch as esterase or lipase, or by treatment with a base such as sodiumhydroxide or potassium hydroxide. In this case, if a protecting group R³for a carboxylic acid at an end of the compound (21A) or (21B) isremoved, the carboxyl group may be protected by an appropriateprotecting group R³ such as methyl group to obtain the compound (21A) or(21B).

[0091] Hereinafter, but not limited to, the present invention will bedescribed by examples.

REFERENCE EXAMPLE 1 Synthesis of o-iodoxybenzoic Acid

[0092] According to a method described in J. Org. Chem., 48, 4155-4156(1983) and Tetrahedron Lett., 35, 8019-8022 (1994), o-iodoxybenzoic acidwas prepared. That is, potassium bromate (76.0 g) was gradually addedinto 0.73 M sulfuric acid solution (730 ml) of 2-iodobeonzoic acid (85.2g) while being stirred strongly for 30 minutes. During this period, thetemperature of the reaction mixture was kept at 55° C. or less. Afterbeing stirred for 3.6 hours at 65° C., the reaction mixture was cooledto 0° C. and then a precipitate was collected by a filtration. Theprecipitate was washed with water (1 litter) and ethanol (50 ml) twotimes, successively, to yield o-iodoxybenzoic acid (89.1 g, 93%).

[0093] Also, for synthesizing o-iodoxybenzoic acid a method described inJ. Org. Chem. 64, 4537-4538 (1999) can be used.

REFERENCE EXAMPLE 2 Synthesis of Jones Regent

[0094] According to a method described in “Jikken Kagaku Koza” vol. 23,4th Ed., edited by the Chemical Society of Japan, a Jones regent wasprepared. That is, to a aqueous solution (10 ml) containing chromiumoxide (VI) (7 g) was added concentrated sulfuric acid (6.1 ml) whilebeing cooled with ice, and then water (20 ml) was further added thereto,thereby preparing Jones regent.

PREPARATION EXAMPLE 1 Synthesis of methyl9-[(tert-butyldimethylsilyl)oxy]-9-(2-oxylanyl)nonanate (Compound 34)

[0095] (i)Methyl 9-oxononanate (Compound 31)

[0096] (Method A)

[0097] To a solution of azelaic acid monomethyl ester (4.04 g) in THF(50 ml) was added 1,1′-carbonyldiimidazole (4.86 g) and then refluxedwith heating for 2 hours. After being cooled, the reaction mixture waspoured into water and extracted with ethyl acetate. The organic layerwas washed with saturated sodium hydrogencarbonate aqueous solution andsaturated brine successively, and then dried over magnesium sulfateanhydride. The solvent was evaporated under reduced pressure to give acrude product (4.71 g).

[0098] To a solution of the crude product (4.71 g) in THF (50 ml) wasdropwise added a solution of lithium aluminum hydrate tri-tert-butoxide(6.1 g) in THF (50 ml) and then stirred for 1.5 hours at roomtemperature. The reaction mixture which volume was reduced to about 50ml by partial evaporation of the solvent under reduced pressure, waspoured into 1N hydrochloric acid (200 ml) and then extracted with ethylacetate. The organic layer was washed with water and saturated brinesuccessively, and then dried over magnesium sulfate anhydride. Thesolvent was evaporated under reduced pressure to give methyl9-oxononanate (3.33 g 89.3%).

[0099] (Method B)

[0100] To a solution of 70% methyl oleate (10.0 g) in dichloromethane(50 ml) was added 70% m-chloroperbenzoic acid (16.63 g) while beingcooled with ice and then stirred for 1 hour at room temperature. To thereaction mixture was added saturated sodium thiosulfate aqueous solutionand then extracted with diethyl ether. The organic layer was washed withsaturated sodium hydrogencarbonate aqueous solution and saturated brinesuccessively, and then dried over sodium sulfate anhydride. The solventwas evaporated under reduced pressure to give a crude product (12.73 g).

[0101] Then, to an aqueous solution (5 ml) containing periodic aciddihydrate (13.3 g) was added a solution of the resulting crude product(12.73 g) in dioxane (25 ml) and then stirred for 1 hour at roomtemperature. The reaction mixture was poured into water and thenextracted with diethyl ether. The organic layer was washed withsaturated brine, dried over sodium sulfate anhydride, and thenevaporated under reduced pressure. The residue was purified by silicagel column chromatography (n-hexane:ethyl acetate=5:1) to give methyl9-oxononanate (3.641 g, 82.8%).

[0102] (Method C)

[0103] A solution of methyl oleate (10.0 g) in methanol (100 ml) waspurged of ozone with stirring at −20° C. for 1 hour. The reactionmixture, with dimethylsulfide (7.43 ml) added thereto at −20° C., wasstirred for 10 minutes and then allowed to warm to room temperature. Theresidue obtained by evaporation of the solvent under reduced pressurewas purified by silica gel column chromatography (n-hexane:ethylacetate=5:1) to give methyl 9-oxononanate (5.65 g, 89.9%).

[0104]¹H-NMR(CDCl₃) δ: 1.22-1.59(10H), 2.28(2H, t, J=7.0 Hz), 2.40(2H,dt, J=1.5, 7.0 Hz), 3.64(3H, s), 9.74(1H, t, J=1.5 Hz).

[0105] (ii)Methyl 9-hydroxy-10-undecenate (Compound 32)

[0106] (Method A)

[0107] To a solution of methyl 9-oxononanate (260.4 mg) in THF (4 ml)was dropwise added 0.95M vinyl magnesium bromide (1.62 ml) at —70° C.and then stirred for 1 hour at −60° C. The reaction mixture was pouredinto a saturated ammonium chloride aqueous solution and then extractedwith ethyl acetate. The organic layer was washed with saturated brine,dried over magnesium sulfate anhydride, and then evaporated underreduced pressure. The residue was purified by silica gel columnchromatography (n-hexane:ethyl acetate=3:1) to give methyl9-hydroxy-10-undecenate (144 mg, 47.4%).

[0108] (Method B)

[0109] To a solution of methyl 9-oxononanate (5.26 g) in THF (60 ml) wasdropwise added 0.95M vinyl magnesium bromide (31.1 ml) at −30° C. andthen stirred for 30 minutes at −25° C. The reaction mixture was pouredinto saturated ammonium chloride aqueous solution and then extractedwith diethyl ether. The organic layer was washed with saturated brine,dried over magnesium sulfate anhydride, and then evaporated underreduced pressure. The residue was purified by silica gel columnchromatography (n-hexane:ethyl acetate=3:1) to give methyl9-hydroxy-10-undecenate (3.41 g, 56.3%).

[0110]¹H-NMR(CDCl₃) δ: 1.27-1.57(12H), 2.26(2H, t, J=7.5 Hz), 3.62(3H),4.04(1H, m), 5.05(1H, d, J=10.0 Hz), 5.17(1H, dd, J=1.5, 10.0 Hz),5.82(1H, m).

[0111] (iii)Methyl 9-hydroxy-9-(2-oxylanyl)nonanate (Compound 33)

[0112] To a solution of methyl 9-hydroxy-10-undecenate (1.669 g) indichloromethane (40 ml) was added m-chloroperbenzoic acid (3.0 g) andsaturated sodium hydrogencarbonate aqueous solution (10 ml)successively. After being stirred for 6 hours at room temperature, thereaction mixture was poured into iced water and then extracted withchloroform. The organic layer was washed with saturated sodiumthiosulfate aqueous solution and saturated brine successively, driedover magnesium sulfate anhydride, and then evaporated under reducedpressure. The residue was purified by silica gel column chromatography(n-hexane:ethyl acetate=3:2) to give methyl9-hydroxy-9-(2-oxylanyl)nonanate (1.212 g, 67.6%)

[0113]¹H-NMR(CDCl₃) δ: 1.29-1.59(12H), 2.27(2H, t, J=7.5 Hz), 2.69 &2.79(total 2H, both m), 2.94 & 2.98(total 1H, both m), 3.40 & 3.79(total1H, both m), 3.64(3H,s).

[0114] (iv)Methyl9-[(tert-butyldimethylsilyl)oxy]-9-(2-oxylanyl)nonanate (Compound 34)

[0115] To a solution of methyl 9-hydroxy-9-(2-oxylanyl)nonanate (1.142g) in dimethylformamide (10 ml) was added tert-butyldimethylchlorosilane(823 mg) and imidazole (743 mg). After being stirred for 60 minutes atroom temperature, the reaction mixture was poured into iced water andthen extracted with ethyl acetate. The organic layer was washed withsaturated sodium hydrogencarbonate aqueous solution and saturated brinesuccessively, dried over magnesium sulfate anhydride, and thenevaporated under reduced pressure. The resulting crude was purified bysilica gel column chromatography (n-hexane:ethyl acetate=20:1) to givethe title compound (687 mg, 40.2%).

[0116]¹H-NMR(CDCl₃) δ: 0.01(3H, s), 0.03 & 0.08(total 3H, both s), 0.85& 0.89(total 9H, both s), 1.28-1.59(12H), 2.27(2H, t, J=7.5 Hz), 2.51 &2.62(total 1H, dd, J=3.0, 5.0 Hz; dd, J=2.5, 5.5 Hz), 2.67 & 2.74(total1H, dd, J=4.0, 5.5 Hz; dd, J=4.0, 4.0 Hz), 2.82 & 2.89(total 1H, bothm), 3.22 & 3.52(total 1H, both m), 3.64(3H, s).

PREPARATION EXAMPLE 2 Synthesis of methyl9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12,15-octadecadiynate(Compound 36)

[0117] (Method A)

[0118] To a solution of 1,4-heptadiyne (17 mg) in THF (8 ml), said diynewas prepared according to a method described in Japanese UnexaminedPatent Publication No.53-34926, was dropwise added 1.5M n-butylithiumsolution in THF (388 μl) at −70° C. and then stirred for 1 hour at −70°C. To the reaction mixture was dropwise added a solution of methyl9-[(tert-butyldimethylsilyl)oxy]-9-(2-oxylanyl)nonanate (85 mg) in THF(2 ml) and boron trifluoride etherate (37 μl) was further added thereto.After being stirred for 1.5 hours at −70° C., the reaction mixture withsaturated ammonium chloride aqueous solution added thereto was extractedwith diethyl ether. The organic layer was washed with saturated brine,dried over magnesium sulfate anhydride, and then evaporated underreduced pressure. The residue was purified by silica gel columnchromatography (n-hexane:ethyl acetate=6:1) to give the title compound(93.7 mg, 87.0%)

[0119] (Method B)

[0120] To a of 1,4-heptadiyne(3.21 g) in THF (80 ml) was dropwise added1.5M n-butyllithium solution in THF (11.61 ml) at −50° C. and thenstirred for 1 hour at −50° C. To the reaction mixture was dropwise addeda solution of methyl9-[(tert-butyldimethylsilyl)oxy]-(2-oxylanyl)nonanate (3.0 g) in THF (10ml) and then boron trifluoride etherate (1.103 ml) was further addedthereto. After being stirred for 1 hour at −50° C., the reaction mixturewith saturated ammonium chloride aqueous solution added thereto wasextracted with diethyl ether. The organic layer was washed withsaturated brine, dried over magnesium sulfate anhydride, and thenevaporated under reduced pressure. The residue was purified by silicagel column chromatography (n-hexane:ethyl acetate=6:1) to give the titlecompound (2.43 g, 63.9%).

[0121]¹H-NMR(CDCl₃) δ: 0.05 & 0.07 & 0.08 & 0.09(total 3H×2, all s),0.87 & 0.88(total 9H, both s), 1.09(3H, t, J=7.5 Hz), 1.08-1.60(12H),2.14(2H, m), 2.28(2H, t, J=7.5 Hz), 2.35(2H, m), 3.10(2H, m),3.58-3.76(2H), 3.64(3H, s).

PREPARATION EXAMPLE 3 Synthesis of9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienic Acid (Compound 40)

[0122] (i)Synthesis of methyl9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12(Z),15(Z)-octadecadienate(Compound 37)

[0123] To a solution of nickel acetate (II) tetrahydrate (49 mg) inmethanol (2 ml) was dropwise added a solution of sodium borohydride (7.4mg) in methanol (2 ml) while being cooled with ice and thenethylenediamine (19 μl) and methyl9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12,15-octadecadiynate (85mg) were added thereto. The reaction mixture was stirred for 40 minutesin a hydrogen gas atmosphere at room temperature and then filtratedthrough Celite 545. The solvent was evaporated from the filtrate underreduced pressure and the residue, with saturated brine added thereto,was extracted with diethyl ether. The organic layer was washed withsaturated brine, dried over magnesium sulfate anhydride, and thenevaporated under reduced pressure. The residue was purified by silicagel column chromatography (n-hexane:ethyl acetate=9:1) to give methyl9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12(Z),15(Z)-octadecadienate(39.2 mg, 45.7%).

[0124]¹H-NMR(CDCl₃) δ: 0.03 & 0.05 & 0.06 & 0.09(total 3H x 2, all s),0.87 & 0.88(total 9H, both s), 0.95(3H, t, J=7.5 Hz), 1.28-1.59(12H),2.04(2H, m), 2.15 & 2.33(total 2H, both m), 2.28(2H, t, J=7.5 Hz), 2.76& 2.88(total 2H, m), 3.45-3.75(2H), 3.64(3H, s), 5.30-5.47(4H).

[0125] (ii)Synthesis of methyl9-[(tert-butyldimethylsilyl)oxy]-10-oxo-12(Z),15(Z)-octadecadienate(Compound 38)

[0126] (Method A)

[0127] To a solution of methyl9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12(Z),15(Z)-octadecadienate(20.5 mg) in dichloromethane (4 ml) was added 1M o-iodoxybenzoic acidsolution in DMSO (0.1 ml) and then stirred for 2 hours at roomtemperature. The reaction mixture, with saturated hydrogencarbonateaqueous solution added thereto, was extracted with diethyl ether. Theorganic layer was washed with saturated brine, dried over magnesiumsulfate anhydride, and then evaporated under reduced pressure. Theresidue was purified by thin-layer silica gel plate (n-hexane:ethylacetate=9:1) to give methyl9-[(tert-butyldimethylsilyl)oxy]-10-oxo-12(Z),15(Z)-octadecadienate (8.9mg, 43.6%).

[0128] (Method B)

[0129] To a solution of methyl9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12(Z),15(Z)-octadecadienate(125 mg) in acetone (3 ml) was added Jones reagent (0.3 ml) and thenstirred for 20 minutes at room temperature. The reaction mixture withsaturated sodium hydrogensulfite aqueous solution added thereto wasextracted with diethyl ether. The organic layer was washed withsaturated hydrogencarbonate aqueous solution and saturated brinesuccessively, dried over magnesium sulfate anhydride, and thenevaporated under reduced pressure to give methyl9-[(tert-butyldimethylsilyl)oxy]-10-oxo-12(Z),15(Z)-octadecadienate (109mg, 87.6%).

[0130]¹H-NMR(CDCl₃) δ: 0.03(3H, s), 0.04(3H, s), 0.91(9H, s), 0.95(3H,t, J=7.5 Hz), 1.26-1.56(12H), 2.04(2H, m), 2.27(2H, t, J=7.5 Hz),2.74(2H, t, J=6.0 Hz), 3.34(2H, dd, J=5.0, 7.0 Hz), 3.64(3H, s),4.03(1H, dd, J=5.5, 7.5 Hz), 5.28(1H, m), 5.38(1H, m), 5.56(2H, m).

[0131] (iii) Methyl 9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienate(Compound 39)

[0132] (Method A)

[0133] Methyl9-[(tert-butyldimethylsilyl)oxy]-10-oxo-12(Z),15(Z)-octadecadienate (2.5mg) was dissolved in a mixed solution (0.5 ml) of 46% hydrogen fluorideaqueous solution:acetonitrile=1:19 and then stirred for 30 minutes atroom temperature. The reaction mixture with saturated hydrogencarbonateaqueous solution, was extracted with diethyl ether. The organic layerwas washed with saturated brine, dried over magnesium sulfate anhydride,and then evaporated under reduced pressure. The residue was purified bythin-layer silica gel plate (n-hexane:ethyl acetate=4:1) to give methyl9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienate (2.0 mg, 100%).

[0134] (Method B)

[0135] To a solution of methyl9-[(tert-butyldimethylsilyl)oxy]-10-oxo-12(Z),15(Z)-octadecadienate (42mg) in acetonitrile (1 ml) was added boron trifluoride etherate (150 μl)while being cooled with ice and then stirred for 3 hours. The reactionmixture with saturated hydrogencarbonate aqueous solution added theretowas extracted with ethyl acetate. The organic layer was washed withsaturated sodium hydrogencarbonate aqueous solution and saturated brinesuccessively, dried over magnesium sulfate anhydride, and thenevaporated under reduced pressure. The residue was purified bythin-layer silica gel plate (n-hexane:ethyl acetate=4:1) to give methyl9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienate (23 mg, 75.8%).

[0136]¹H-NMR(CDCl₃) δ: 0.96(3H, t, J=7.5 Hz), 1.23-1.80(12H), 2.04(2H,m), 2.28(2H, t, J=7.5 Hz), 2.76(2H, t, J=7.5 Hz), 3.25(2H, t, J=8.0 Hz),3.36(1H, d J=5.0 Hz), 3.64(3H, s), 4.21(1H, m), 5.26(1H, m), 5.41(1H,m), 5.54(1H, m), 5.60(1H, m).

[0137] (iv) 9-Hydroxy-10-oxo-12(Z),15(Z)-octadecadienic Acid (Compound40)

[0138] (Method A)

[0139] Methyl 9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienate (1.0 mg) andTween 80 (1.0 mg) were dissolved in 40 mM phosphate buffer pH 7.0 (0.5ml). The solution, with lipase (Sigma XIV, Sigma Chemical Co.) (3.0 mg)added thereto, was placed for 24 hours at 37° C. The reaction mixturewas purified by high-performance liquid chromatography (ODS column,acetonitrile:water=1:1 including 0.01% TFA) to give the title compound(0.6 mg, 60%).

[0140] (Method B)

[0141] Methyl 9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienate (12 mg) wasdissolved in a mixed solution (1 ml) of 0.1M phosphate buffer pH7.0:acetone=9:1. The solution, with Lipase PS (AMANO SEIYAKU Co., Ltd.)(12 mg) added thereto, was stirred for 30 minutes at room temperature.The reaction mixture was poured into water and extracted with ethylacetate. The organic layer was washed with saturated brine, dried oversodium sulfate anhydride, and then evaporated under reduced pressure togive the title compound (5.8 mg, 50.5%).

[0142]¹H-NMR(CD₃OD) δ: 0.97(3H, t, J=7.5 Hz), 1.28-1.71(12H), 2.08(2H,m), 2.26(2H, t, J=7.5 Hz), 2.79(2H, m), 3.35(2H, t, J=5.0 Hz), 4.10(1H,m), 5.29(1H, m), 5.40(1H, m), 5.54(2H, m).

PREPARATION EXAMPLE 4 Synthesis of9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienic Acid (Compound 40)

[0143](i)9-[(tert-Butyldimethylsilyl)oxy]-10-hydroxy-12(Z),15(Z)-octadecadienicAcid (Compound 41)

[0144] Methyl9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12(Z),15(Z)-octadecadienate(16.0 mg) obtained in Preparation Example 3 (i) was dissolved in a mixedsolution (1 ml) of 5% potassium hydroxide solution in methanol:water=3:1and stirred for 45 minutes at room temperature. The reaction mixture wasneutralized with 1N hydrochloric acid, and then extracted with diethylether. The organic layer was washed with saturated brine, dried overmagnesium sulfate anhydride, and then evaporated under reduced pressure.The residue was purified by thin-layer silica gel plate(n-hexane:acetone=2:1) to give9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12(Z),15(Z)-octadecadienicacid (15.1 mg, 100%).

[0145]¹H-NMR(CDCl₃) δ: 0.08(3H), 0.09 & 0.10(total 3H, both s), 0.91 &0.92(total 9H, both s), 0.98(3H, t, J=7.5 Hz), 1.27-1.65(12H), 2.07(2H,m), 2.18-2.34(2H), 2.36(2H, t, J=7.5 Hz), 2.81 & 2.91(total 2H, both m),3.42-3.76(2H), 5.35-5.49(4H).

[0146] (ii)Synthesis of9-[(tert-butyldimethylsilyl)oxy]-10-oxo-12(Z),15(Z)-octadecadienic Acid(Compound 42)

[0147] To a solution of9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12(Z),15(Z)-octadecadienicacid (15.1 mg) in dichloromethane (1 ml) was added 1M o-iodoxybenzoicacid in DMSO (0.1 ml) and stirred for 1 hour at room temperature. Thereaction mixture, with water added thereto, was extracted with diethylether. The organic layer was washed with saturated brine, dried overmagnesium sulfate anhydride, and then evaporated under reduced pressure.The residue was purified by thin-layer silica gel plate (n-hexane:ethylacetate=2:1) to give9-[(tert-butyldimethylsilyl)oxy]-10-oxo-12(Z),15(Z)-octadecadienic acid(6.8 mg, 45.2%).

[0148]¹H-NMR(CDCl₃) δ: 0.03(3H, s), 0.04(3H, s), 0.91(9H, s), 0.95(3H,t, J=7.5 Hz), 1.24-1.61(12H), 2.04(2H, m), 2.32(2H, t, J=7.5 Hz),2.74(2H, m), 3.34(2H, t, J=5.0 Hz), 4.03(1H, m), 5.28(1H, m), 5.39(1H,m), 5.56(2H, m).

[0149] (iii) 9-Hydroxy-10-oxo-12(Z),15(Z)-octadecadienic Acid (Compound40)

[0150]9-[(tert-Butyldimethylsilyl)oxy]-10-oxo-12(Z),15(Z)-octadecadienic acid(3.4 mg) was dissolved in a mixed solution (0.5 ml) of 46% hydrogenfluoride aqueous solution:acetonitrile=1:19 and then stirred for 30minutes at room temperature. The reaction mixture, with water addedthereto, was extracted with diethyl ether. The organic layer was washedwith saturated brine ten times, dried over magnesium sulfate anhydride,and then evaporated under reduced pressure. The residue was purified bythin-layer silica gel plate (n-hexane:ethyl acetate=1:1) to give thetitle compound (1.5 mg, 60.4%).

[0151] In addition, as a typical example of an optically active α-ketolunsaturated fatty acid, a synthetic example of(R)-9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienic acid (Compound 40A) willbe described in below. The ¹H-NMR data of each compounds is same as thatof the corresponding racemate. With respect to compound 32A, it wasverified by New Mosher method that its 9-position had R-configuration.Also, since an optical rotation of compound 40A which was finallyproduct was same as an authentic sample, it was verified that 9-positionof each compounds had R-configuration.

PREPARATION EXAMPLE 5 Synthesis of(R)-9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienic Acid (Compound 40A)

[0152] (i)(R)-Methyl 9-hydroxy-10-undecenate (Compound 32A)

[0153] (Method A)

[0154] To a solution of methyl 9-hydroxy-10-undecenate (500 mg) indiisopropyl ether (12 ml) was added vinyl acetate (323 μl) and Lipase PS(AMANO SEIYAKU Co., Ltd.) (500 mg) and then shaken for 62 hours at 30°C. The reaction mixture was filtrated and the filtrate was poured intoethyl acetate. The organic layer was washed with saturated brine, driedover magnesium sulfate anhydride, and then evaporated under reducedpressure. The resulting product was purified by silica gel columnchromatography (n-hexane:ethyl acetate=3:1) to give (R)-methyl9-hydroxy-10-undecenate (152 mg, 30.4%).

[0155] (Method B)

[0156] To a solution of methyl 9-hydroxy-10-undecenate (509 mg) inpentane (12 ml) was added vinyl acetate (1.097 ml) and Lipase PS (AMANOSEIYAKU Co., Ltd.) (238 mg) and then shaken for 62 hours at 30° C. Thereaction mixture was filtrated and the filtrate was poured into ethylacetate, washed with saturated brine, dried over magnesium sulfateanhydride, and then evaporated under reduced pressure. The resultingproduct was purified by silica gel column chromatography (n-hexane:ethylacetate=3:1) to give (R)-methyl 9-hydroxy-10-undecenate (168 mg, 33.6%).

[0157] (Method C)

[0158] To a solution of methyl 9-hydroxy-10-undecenate (9.38 g) inpentane (150 ml) was added vinyl acetate (4.037 ml) and Lipase PS (AMANOSEIYAKU Co., Ltd.) (2.190 g) and then shaken at 30° C. After 48 hours,the reaction was stopped and the reaction mixture was filtrated. Thefiltrate was poured into ethyl acetate, washed with saturated brine,dried over magnesium sulfate anhydride, and then evaporated underreduced pressure. The resulting product was purified by silica gelcolumn chromatography (n-hexane:ethyl acetate=5:2) to give methyl9-hydroxy-10-undecenate (5.999 g, 64.0%) as a mixture ofR-isomer:S-isomer=2:1. When the reaction is stopped halfway like thiscase, it is possible to control a ratio between R- and S-isomer freely.

[0159] (Method D)

[0160] To a solution of methyl 9-hydroxy-10-undecenate (5.293 g) inpentane (100 ml) was added vinyl acetate (11.38 ml) and Lipase PS (AMANOSEIYAKU Co., Ltd.) (1.235 g) and then shaken for 72 hours at 30° C. Thereaction mixture was filtrated and the filtrate was poured into ethylacetate, washed with saturated brine, dried over magnesium sulfateanhydride, and then evaporated under reduced pressure. The resultingproduct was purified by silica gel column chromatography (n-hexane:ethylacetate=5:2) to give (R)-methyl 9-hydroxy-10-undecenate (1.937 g,36.7%).

Determination of Compound 32A's Configuration by New Mosher Method

[0161]

[0162] (1)Synthesis of (S)-MTPA ester(32A-1) of Compound 32A

[0163] To a solution of (S)-2-methoxy-2-trifluoromethylphenylacetic acid((S)-MTPA) (15 mg) in dichloromethane (1 ml) was added1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (15 ml),4-dimethylaminopyridine (10 mg) and compound 32A (5 mg) and then stirredfor 5 hours at room temperature. The reaction mixture was poured intowater and then extracted with ethyl acetate. The organic layer waswashed with 5% hydrochloric acid, saturated hydrogencarbonate aqueoussolution, and saturated brine successively, dried over magnesium sulfateanhydride, and then evaporated under reduced pressure. The residue waspurified by thin-layer silica gel plate (n-hexane:ethyl acetate=4:1) togive compound 32A-1 (4 mg, 39.8%).

[0164]¹H-NMR(CDCl₃) δ: 1.26-1.72 (12H), 2.2941 (2H, t, J=7.5 Hz, 2-H),3.55 (3H), 3.66 (3H), 5.19 (1H, d-like, J=10.5 Hz), 5.25 (1H, d-like,J=17.5 Hz), 5.43 (1H, m), 5.7205 (1H, m, 10-H), 7.38-7.52 (5H).

[0165] (2)Synthesis of (R)-MTPA ester(32A-2) of Compound 32A

[0166] Using (R)-2-methoxy-2-trifluoromethylacetic acid(i.e., (R)-MTPA),in a same manner to compound 32A-1, compound 32A-2 was prepared.

[0167]¹H-NMR(CDCl₃) δ: 1.23-1.70 (12H), 2.2867 (2H, t, J=7.5 Hz, 2-H),3.55 (3H), 3.66 (3H), 5.25 (1H, dd, J=1.0, 10.5 Hz), 5.35 (1H, dd,J=1.0, 17.5 Hz), 5.45 (1H, m), 5.8167 (1H, m, 10-H), 7.37-7.53 (5H).

[0168] (3)Determination of 9-Configuration of Compound 32A

[0169] It is known that the configuration of secondary hydroxyl groupcan be determined by application of New Mosher Method (Journal ofAmerican Chemical Society, 113, 4092 (1991)).

[0170] As a result in application of this method to compound 32A, Δδvolumes were −0.0962 and +0.0074 at 10- and 2-position respectively. TheΔδ volume was calculated by using ¹H-NMR data of each MTPA esters ofcompound 32A (i.e., compound 32A-1 and 32A-2) according to the followingequation:

Δδ=δ(Compound 32A-1)−δ(Compound 32A-2).

[0171] Due to this, it could be verified that 9-position of compound 32Ahad R-configuration.

[0172] (ii)Synthesis of (R)-methyl 9-hydroxy-9-(2-oxylanyl)nonanate(Compound 33A)

[0173] To a solution of (R)-methyl 9-hydroxy-10-undecenate (6.81 g) indichloromethane (90 ml) was added m-chloroperbenzoic acid (70% purity,including moisture, manufactured by WAKO PURE CHEMICAL INDUSTRIES Ltd.)(15.67 g) and then stirred for 2 hours at room temperature. To thereaction mixture concentrated to about 30 ml by removing the solventunder reduced pressure was dropwise added saturated sodium thiosulfateaqueous solution while being cooled with ice. This mixture was extractedwith diethyl ether and the extract was washed with saturatedhydrogencarbonate aqueous solution and saturated brine successively,dried over magnesium sulfate anhydride, and then evaporated underreduced pressure to give (R)-methyl 9-hydroxy-9-(2-oxylanyl) nonanate(7.414 g, 100%).

[0174] (iii)Synthesis of (R)-methyl9-[(tert-butyldimethylsilyl)oxy]-9-(2-oxylanyl) nonanate (Compound 34A)

[0175] (Method A)

[0176] To a solution of (R)-methyl 9-hydroxy-9-(2-oxylanyl)nonanate (166mg) in dimethylformamide (3 ml) was added tert-butyldimethylchlorosilane(217 mg) and imidazole (196 mg), and then stirred for 18 hours at roomtemperature. The reaction mixture was poured into iced water and thenextracted with ethyl acetate. The organic layer was washed withsaturated sodium hydrogencarbonate aqueous solution and saturated brinesuccessively, dried over magnesium sulfate anhydride, and thenevaporated under reduced pressure. The crude resultant was purified bysilica gel column chromatography (n-hexane:ethyl acetate=10:1) to give(R)-methyl 9-[(tert-butyldimethylsilyl)oxy]-9-(2-oxylanyl)nonanate(185.1 mg, 74.5%).

[0177] (Method B)

[0178] To a solution of (R)-methyl 9-hydroxy-9-(2-oxylanyl)nonanate(7.414 g) in dimethylformamide (70 ml) was addedtert-butyldimethylchlorosilane (9.65 g) and imidazole (8.77 g), and thenstirred for 18 hours at room temperature. The reaction mixtureconcentrated to about 30 ml by removing the solvent under reducedpressure was poured into iced water and extracted with ethyl acetate.The organic layer was washed with 5% hydrochloric acid, saturated sodiumhydrogencarbonate aqueous solution and saturated brine successively,dried over magnesium sulfate anhydride, and then evaporated underreduced pressure. The crude resultant was purified by silica gel columnchromatography (n-hexane:ethyl acetate=10:1) to give (R)-methyl9-[(tert-butyldimethylsilyl)oxy]-9-(2-oxylanyl)nonanate (2.994 g,27.0%).

[0179] (iv) Synthesis of (R)-methyl9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12,15-octadecadiynate(Compound 36A)

[0180] To a solution of 1,4-heptadiyne (3.14 g) in THF (20 ml) wasdropwise added 1.5M n-butyllithium solution in THF (10.7 ml) at −70° C.and then stirred for 45 minutes at −70° C. To the reaction mixture wasdropwise added a solution of (R)-methyl9-[(tert-butyldimethylsilyl)oxy]-9-(2-oxylanyl)nonanate (2.83 g) in THF(5 ml) and further added boron trifluoride etherate (1.19 ml). Afterbeing stirred for an additional 1 hour at −70° C., the reaction mixturewith saturated ammonium chloride aqueous solution added thereto wasextracted with diethyl ether. The extract was washed with saturatedbrine, dried over magnesium sulfate anhydride, and then evaporated underreduced pressure, to give (R)-methyl9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12,15-octadecadiynate (4.18g, 100%).

[0181] (v) Synthesis of (R)-methyl9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12(Z),15(Z)-octadecadienate(Compound 37A)

[0182] To a solution of (R)-methyl9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12,15-octadecadiynate (3.96g) in toluene (30 ml) was added Lindlar catalyst (palladium, 5 wt % onCaCO₃, poisoned with lead) (200 mg) and stirred for 1 hour at roomtemperature in a hydrogen gas atmosphere. The reaction mixture wasfiltrated through Celite 545 and the filtrate with saturated brine addedthereto was extracted with ethyl acetate. The organic layer was washedwith saturated brine, dried over magnesium sulfate anhydride, and thenevaporated under reduced pressure. The crude resultant was purified bysilica gel column chromatography (n-hexane:ethyl acetate=9:1) to give(R)-methyl9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12(Z),15(Z)-octadecadienate(2.427 g, 60.7%).

[0183] (vi)Synthesis of (R)-methyl9-[(tert-butyldimethylsilyl)oxy]-10-oxo-12(Z),15(Z)-octadecadienate(Compound 38A)

[0184] To a solution of (R)-methyl9-[(tert-butyldimethylsilyl)oxy]-10-hydroxy-12(Z),15(Z)-octadecadienate(2.312 g) in acetone (20 ml) was added dropwise slowly Jones regent (5.0ml) while being cooled with ice and stirred for 40 minutes at roomtemperature. The reaction mixture with saturated sodium hydrogensulfiteaqueous solution added thereto was extracted with diethyl ether. Theorganic layer was washed with saturated hydrogencarbonate aqueoussolution and saturated brine successively, dried over magnesium sulfateanhydride, and then evaporated under reduced pressure to give (R)-methyl9-[(tert-butyldimethylsilyl)oxy]-10-oxo-12(Z),15(Z)-octadecadienate(2.222 g, 96.5%).

[0185] (vii) Synthesis of (R)-methyl9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienate (Compound 39A)

[0186] To a solution of (R)-methyl9-[(tert-butyldimethylsilyl)oxy]-10-oxo-12(Z),15(Z)-octadecadienate(2.20 g) in acetonitryl (20 ml) was added boron trifluoride etherate(539 μl) while being cooled with ice and then stirred for 35 minutesunder the same cooled condition. The reaction mixture with saturatedhydrogencarbonate aqueous solution added thereto was extracted withdiethyl ether. The organic layer was washed with saturatedhydrogencarbonate aqueous solution and saturated brine successively,dried over magnesium sulfate anhydride, and then evaporated underreduced pressure. The residue was purified by silica gel columnchromatography (n-hexane:ethyl acetate=4:1) to give (R)-methyl9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienate (447.4 mg, 27.5%).

[0187] (viii)Synthesis of(R)-9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienic Acid (Compound 40A)

[0188] (R)-Methyl 9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienate (387.4mg) was dissolved in a mixed solution (6 ml) of 0.1M phosphate buffer(pH 7.0) :acetone=1:1. To the solution was added Lipase PS (AMANOSEIYAKU Co., Ltd.) (40 mg) and stirred for 15 hours at room temperature.The reaction mixture was poured into water and extracted with ethylacetate. The organic layer was washed with saturated brine, dried oversodium sulfate anhydride, and then evaporated under reduced pressure togive the title compound (373.8 mg, 100%).

Comparative Example 1

[0189]

[0190] To a solution of samarium diiodide (40 mg) in acetonitrile (1 ml)was added a solution of compound (31) (60 mg) in acetonitrile (1 ml) andfurther added a solution of compound (51) (40 mg) in acetonitrile (2ml). After stirring for 20 minutes at room temperature, the reactionmixture with 1N hydrochloric acid (10 ml) added thereto was extractedwith diethyl ether. The organic layer was washed with 10% sodiumthiosulfate aqueous solution, dried over magnesium sulfate anhydride,and then evaporated under reduced pressure. The residue was purified bysilica gel column chromatography (n-hexane:ethyl acetate=5:1) to givecompound (52) (13.2 mg, 17.6%), but the aimed Compound 39 could not beisolated.

[0191]¹H-NMR(CDCl₃) δ: 0.97(3H, t, J=7.5 Hz), 1.25-1.79(14H), 2.05(2H,m), 2.30(2H, t, J=7.5 Hz), 2.41(2H, m), 3.64(3H, s), 4.34(1H, m),5.29(1H, m), 5.43(1H, m), 6.24(1H d, J=16.0 Hz), 7.03(1H, dt, J=16.0,6.5 Hz).

Comparative Example 2

[0192]

[0193] To a solution of compound (53) (110 mg) in THF (4 ml) was addedhexamethylphosphoramido (HMPA) (10 mg). After being cooled to −60° C.,the mixture with 1.5M n-butyllithium solution in THF (386 μl) dropwiseadded thereto was stirred at −20° C. for 30 minutes. To the reactionmixture was dropwise added a solution of compound (31) (179 mg) in THF(5 ml) and then stirred for 15 minutes at −20° C. The reaction mixturewith saturated ammonium chloride aqueous solution was extracted withdiethyl ether. The organic layer was washed with saturated brine, driedover magnesium sulfate anhydride, and then evaporated under reducedpressure. The resultant was a complicated mixture and the aimed compound(54) could not be isolated.

Comparative Example 3

[0194]

[0195] To a solution of compound (55) (53.7 mg) in THF (3.5 ml) wasadded 1.5M n-butyllithium solution in THF (133 μl) dropwise addedthereto and stirred for 1 hour at a temperature in the range of −60° C.to −30° C. To the reaction mixture was dropwise added a solution ofCompound 56 (49.8 mg) in THF (3 ml) at −30° C. and then stirred at −30°C. for 1 hour. The reaction mixture with saturated ammonium chlorideaqueous solution was extracted with diethyl ether. The organic layer waswashed with saturated brine, dried over magnesium sulfate anhydride, andthen evaporated under reduced pressure. The residue was purified bysilica gel column chromatography (n-hexane:ethyl acetate=3:1) to givecompound (57) (13.5 mg, 15.5%).

[0196]¹H-NMR(CDCl₃) δ: 0.95(3H, t, J=7.5 Hz), 1.30-1.60(14H), 2.02(2H,m), 2.38(3H, s), 2.39(2H, m), 2.44(3H, s), 2.72 & 2.77(total 2H, bothm), 3.82(2H, m), 3.92(2H, m), 4.05 & 4.14(total 1H, m), 4.81(1H, t,J=4.5 Hz), 5.25(1H, m), 5.37(2H, m), 5.48(1H, m), 7.33(2H, d, J=8.0 Hz),7.84(2H, d, J=8.0 Hz).

[0197] Compound (57) (3.8 mg) was dissolved in a mixed solution (1 ml)of concentrated hydrochloric acid:methanol=7:100 and refluxed for 1 hourwith heating. The reaction mixture was neutralized through ion exchangeresin (Amberlite IRA-68, OH⁺ form) and the solvent was evaporated underreduced pressure. The resultant was a complicated mixture and the aimedcompound (58) could not be isolated.

[0198] As described in the foregoing, by the synthetic method of thepresent invention α-ketol unsaturated fatty acid wherein a double bondexists at β-position to a ketone group can be efficiently prepared,thereby improving the yield thereof.

We claim
 1. A method of synthesizing an α-ketol unsaturated fatty acidcomprising the steps of: preparing compound (4) by reactingmonosubstituted acetylene (2) with epoxide (3); and preparing α-ketolunsaturated fatty acid (1) from said compound (4), as shown in ReactionFormula 1:

 wherein R¹ represents an alkyl group of 1-18 carbon atoms or analiphatic hydrocarbon group of 2-18 carbon atoms having 1-5 double ortriple bonds at given positions; R² represents a protecting group for ahydroxyl group; R³ represents a protecting group for a carboxyl group; Ris identical to R¹ or, when R¹ has one or more triple bonds, Rrepresents an aliphatic hydrocarbon group in which each triple bond ofR¹ is converted to a double bond; and A represents an alkylene group of1-18 carbon atoms.
 2. The method according to claim 1 comprising thesteps of: reducing said compound (4) to produce compound (5); oxidizinga hydroxyl group of said compound (5) to produce compound (6); anddeprotecting R² and R³ of said compound (6) to produce said α-ketolunsaturated fatty acid (1), as shown in Reaction Formula 2:

wherein R¹, R², R³, R, and A are the same as defined in said ReactionFormula
 1. 3. The method according to claim 1 comprising the steps of:reducing said compound (4) to produce compound (5); deprotecting R³ ofsaid compound (5) to produce compound (7); oxidizing a hydroxyl group ofsaid compound (7) to produce compound (8); and deprotecting R² of saidcompound (8) to produce said α-ketol unsaturated fatty acid (1), asshown in Reaction Formula 3:

wherein R¹, R², R³, R, and A are the same as defined in said ReactionFormula
 1. 4. The method according to any of claims 1 to 3, wherein R¹represents R⁴—C≡C—CH₂—, where R⁴ represents an alkyl group of 1-7 carbonatoms.
 5. The method according to claim 4, wherein R⁴ represents ethylgroup.
 6. The method according to any of claims 1 to 5, wherein Arepresents an alkylene group expressed by —(CH₂)n—, where n is aninteger of 1 to
 10. 7. The method according to claim 6, wherein n isequal to
 7. 8. The method according to any of claims 1 to 7, wherein R²represents an ether-type protecting group.
 9. The method according toany of claims 1 to 8, wherein the double bond of α-ketol unsaturatedfatty acid (1) has a cis-configuration.
 10. An intermediate forsynthesis of α-ketol unsaturated fatty acid (1) described in any ofclaims 1 to 9, represented by the general formula (4):

wherein R¹ represents an alkyl group of 1-18 carbon atoms or analiphatic hydrocarbon group of 2-18 carbon atoms having 1-5 double ortriple bonds at given positions; R² represents a protecting group for ahydroxyl group; R³ represents a protecting group for a carboxyl group;and A represents an alkylene group of 1-18 carbon atoms.
 11. The methodaccording to any of claims 1 to 9, which is a method of synthesizing anoptically active α-ketol unsaturated fatty acid, wherein an asymmetriccarbon atom of —C(OR²)— in said epoxide (3) has either ofR-configuration or S-configuration, and an asymmetric carbon atom in theα-ketol structure of said α-ketol unsaturated fatty acid (1) has eitherof R-configuration or S-configuration.
 12. The method according to claim11 comprising the steps of: preparing compound (4A) by reacting saidmonosubstituted acetylene (2) with (R)-epoxide (3A) obtained fromcompound (21A) which asymmetric carbon atom at an aryl position hasR-configuration; and preparing (R)-α-ketol unsaturated fatty acid (1A)from said compound (4A), as shown in Reaction Formula 1A:

wherein R¹, R², R³, R, and A are the same as defined in said ReactionFormula
 1. 13. The method according to claim 11 comprising the steps of:preparing compound (4B) by reacting said monosubstituted acetylene (2)with (S)-epoxide (3B) obtained from compound (21B) which asymmetriccarbon atom at an aryl position has S-configuration; and preparing(S)-α-ketol unsaturated fatty acid (1B) from said compound (4B), asshown in Reaction Formula 1B:

wherein R¹, R², R³, R, and A are the same as defined in said ReactionFormula
 1. 14. An optically active intermediate for synthesis of α-ketolunsaturated fatty acid (1A) or (1B) described in any of claims 11 to 13,represented by the general formula (4A) or (4B):

wherein R¹ represents an alkyl group of 1-18 carbon atoms or analiphatic hydrocarbon group of 2-18 carbon atoms having 1-5 double ortriple bonds at given positions; R² represents a protecting group for ahydroxyl group; R³ represents a protecting group for a carboxyl group;and A represents an alkylene group of 1-18 carbon atoms.